1. Field of the Invention
The present invention relates to a vane type hydraulic actuator for use, for example, in a valve timing adjusting apparatus, which controls the timing of opening and closing of an intake valve and/or exhaust valve of an engine, in response to the running condition of the engine.
2. Description of the Prior Art
FIG. 23 is a cross sectional view of a vane type hydraulic actuator of the prior art, specifically, it is a vane type hydraulic actuator shown in Japanese Patent Application JP-A-314069 applied by the same applicant of this patent application. FIG. 24 is a detailed cross sectional view of the plunger portion of the actuator shown in FIG. 23, which is a main portion of the actuator. FIG. 25 is a cross sectional view of the plunger portion shown in FIG. 24, at a state when an oil pressure is applied.
Reference numeral 19 denotes a cam shaft for an intake valve having a cam for the intake valve 19a. A timing pulley 21 is disposed at an end portion of the cam shaft 19. An actuator for valve timing adjusting is connected with the cam shaft 19. The working oil of the actuator 40 is the lubrication oil of the engine (not shown). The actuator 40 functions to change the biasing angle of the cam shaft 19 so as to change continuously the timing of the opening and closing of the intake valve (not shown). Reference numeral 41 is a bearing for the cam shaft 19, and reference numeral 42 denotes the housing of the actuator 40, which can rotate relatively to the cam shaft for the intake valve 19.
A case 43 is fixed to the housing 42, which accommodates a vane type rotor 44 therein. The rotor 44 is fixed to the cam shaft 19 by a bolt 45, and can rotate relatively to the case 43.
A chip seal 46 is disposed between the case 43 and the rotor 44, for preventing the leakage of working oil between chambers limited by the case 43 and the rotor 44. For this purpose, the chip seal 46 is urged by a plate spring 47 to contact tightly with the rotor 44.
A cover 28 is fixed to the case 43. The housing 42, the case 43 and the cover 48 are commonly fastened by a bolt 49. Reference numerals 50, 51, and 52 denote an O-ring, a plate, and a bolt, respectively. Reference numerals 53, 54 denote O-rings. A cylindrical holder 55 is disposed in the rotor 44. The holder has an engaging hole 55a extending in the longitudinal direction of a plunger 56 so as to engage with the plunger 56.
The plunger 56 can slide in the housing 42, and has an engaging shaft portion 56a, which can enter into the engaging hole 55a of the holder 55 and can engage with it. The plunger 56 is urged by a spring 57 towards the holder 55. A working oil is introduced into the engaging hole 55a through a plunger oil channel 58.
When a working oil is introduced into the engaging hole 55a, the plunger 56 moves against the spring 57, so that the locking between the holder 55 and the plunger 56 is released. Reference numerals 59, 61 denote air holes. Reference numeral 60 denotes a shaft bolt rotatable relatively to the cover 48.
A first oil channel 62 and a second oil channel 63 extend through the cam shaft for the intake valve 19 and through the rotor 44. The first oil channel 62 communicates with an oil pressure chamber for timing retard (retarding chamber) 73, which serves to rotate the rotor 44 in the timing retard direction. The second oil channel 63 communicates with an oil pressure chamber for timing advance (advancing chamber) 74, which serves to rotate the rotor 44 in the timing advance direction. In this specification and the claims, the "timing retard direction" means the direction to increase the volume of the oil pressure chamber for timing retard 73, the counterclockwise direction in FIG. 26, and the "timing advance direction" means the direction to increase the volume of the oil pressure chamber for timing advance 74, the clockwise direction in FIG. 26. Both the pressure chambers 73, 74 will be explained later.
The working oil for the actuation of the actuator 40 is supplied through an oil control valve 80 (hereinafter called OCV), which controls the amount of oil to be sent to the actuator 40. The OCV 80 comprises a valve housing 81, a spool 82, which can slide in the valve housing 81, a spring 83 urging the spool 82 and a linear solenoid 84 to move the spool 82 against the biasing force of the spring. The working oil is supplied from a lubrication oil supplying apparatus, which is provided for supplying lubrication oil to each part of engine (not shown). The lubrication oil supplying apparatus is comprised of an oil pan 91, an oil pump 92 and an oil filter 93. The inlet port of the OCV 80 is connected with the oil filter 93 through an oil supply piping 85a. The outlet ports of the OCV 80 are connected with the first and second oil channels 62, 63 through a first piping 89 and a second piping 90. The working oil returns to the oil pan 91 through a drain piping 88. They constitute a working oil supplying apparatus to the actuator 40 together with the oil control valve OCV 80.
An electronic control unit 100 (hereinafter called ECU) controls an injector, an igniter, which are not shown, and the OCV 80, on the basis of signals from an intake air amount sensor, a throttle sensor, a water temperature sensor, a crank angle sensor, and a cam angle sensor, which are not shown. Thus, the ECU controls the fuel injection amount, the timing of the ignition, the timing of opening of the OCV 80 and the timing of the closing of the OCV 80 after the cut off of the ignition switch.
FIG. 26 is a cross sectional view of FIG. 23 along the line X--X. FIG. 27 is a cross sectional view in part, showing a state that a slide plate in FIG. 26 is displaced. FIG. 28 is a cross sectional view of FIG. 23 along the line Y--Y. FIG. 29 is a cross sectional view of FIG. 23 along the line Z--Z.
The rotor 44 has first to fourth vanes 64-67 projecting outwardly in the radial direction. The tips of the vanes 64-67 slide along the inner surface of the case 43, contacting with it. A chip seal 68, as a sealing element is disposed at the contacting portion of each vane 64-67. A back spring (not shown) is disposed between the vane 64-67 and the chip seal 68 so as to urge the chip seal towards the inner surface of the case 43, which is the counter surface of the chip seal. Shoes 71 are provided in the case 43, which are portions jutting inwardly at the inner surface of the case 43. A bolt hole 72 is disposed in the shoes 72, through which the bolt 49 shown in FIG. 23 is inserted.
The tip of each shoe 71 slides along the outer surface of a vane supporting portion 69, contacting with it. The vane supporting portion 69 supports the vanes.
Each space contoured by the inner surface of case 43 and the outer surface of the rotor 44 and limited by neighboring shoes 71 are divided by a vane 64-67 into an oil pressure chamber for timing retard 73 and an oil pressure chamber for timing advance 74. The oil pressure chamber for timing retard 73 serves to rotate the vanes in the timing retard direction, and the oil chamber for timing advance 74 serves to rotate the vanes in the timing advance direction. The cross section of each oil chamber 73, 74 has a substantially fan like form.
The oil pressure chamber for timing retard 73 and the oil pressure chamber for timing advance 74 are connected by a communicating channel 75. A groove 76, with which the plunger oil channel 58 communicates, is disposed in the communicating channel 75.
The communicating channel 75 is separated by a slide plate 77 disposed in this groove 76. The slide plate 77 prevents the oil leakage between the oil chamber for timing retard 73 and the oil chamber for timing advance 74.
The slide plate 77 is movable in this groove 76. When the pressure in the oil pressure chamber for timing retard is higher, the slide plate 77 moves towards the oil pressure chamber for timing advance, as shown in FIG. 26. On the other hand, when the pressure in the oil pressure chamber for timing advance is higher, the slide plate 77 moves towards the oil pressure chamber for timing retard 73, as shown in FIG. 27.
The arrows in FIGS. 26, 28, 29 show the rotation direction of the actuator 40 as a whole.
The oil pressure chamber for timing retard 73 and the oil pressure chamber for timing advance 74 are contoured by the housing 42, the case 43, rotor 44 and the cover 48. The oil pressure chamber for timing retard 73 is communicated with the first oil channel 62, through which the working oil is supplied. The oil pressure chamber for timing advance 74 is communicated with the second oil channel 63, through which the working oil is supplied. The rotor 44 rotates relatively to the housing 42, and the volumes of the oil pressure chambers 73, 74 change, in response to the oil amounts supplied into the oil pressure chambers 73, 74.
The functions of the actuator 40 and the oil control valve 80 are explained below.
When the engine is stopping, the rotor 44 is at the maximum timing retard position, as shown in FIG. 26. Namely, the rotor 44 is rotated relatively to the housing 42 up to the maximum timing advance position. The volume of the oil pressure chamber for timing retard is at the maximum. As the oil pump 92 is stopping, no working oil is supplied neither to the first oil channel 62 nor to the second oil channel 63. Therefore, no working oil is supplied into the plunger oil channel 58, and the oil pressure in the actuator 40 is low. As a result, the plunger 56 is pressed toward the holder 55 by the biasing force of the spring 57, so that the engaging shaft portion 56a of the plunger 56 engages with the engaging hole 55a of the holder 55, namely, the housing 42 and the rotor 44 are engaging to each other.
When the engine begins to run starting from this state, the oil pump 92 works to increase the pressure of the working oil to be supplied to the OCV 80. Then a working oil is supplied into the timing retard oil pressure chamber 73 in the actuator 40 via the first piping 89 and the first oil channel 62. The oil pressure in the timing retard oil pressure chamber 73 causes a displacement of the slide plate 77 towards the timing advance oil pressure chamber 74. Therefore, the oil pressure chamber for timing retard 73 and the plunger oil chamber 58 communicates to each other so that the working oil is supplied into the engaging hole 55a of the holder 55 via the plunger oil channel 58. As a result, the plunger 56 is pressed and is forced to move against the biasing force of the spring 57, so that the engaging shaft portion 56a of the plunger 56 go out from the engaging hole 55a of the holder 55. Namely, the locking between the plunger 56 and the rotor 44 is released.
Because a working oil is supplied into the oil pressure chamber for timing retard 73, the vanes 64-67 of the rotor 44 are pressed against the shoes 71 from the timing retard direction. Therefore, the housing 42 and the rotor 44 press to each other due to the oil pressure in the oil pressure chamber for timing retard 73, even after the locking between the plunger 56 and the rotor 44 is released. As result, the vibration of the rotor or the bumping between them do not occur.
When the rotor 44 shall be rotated in the timing advance direction, a working oil is supplied into the oil pressure chamber for timing advance 74, via the second piping 90 and the second oil channel 63, under the control of the oil control valve 80. The oil pressure in the oil pressure chamber for timing advance 74 causes to displace the slide plate 77 towards the oil pressure chamber for timing retard 73. As a result, the plunger oil channel 58 communicates with the oil pressure chamber for timing advance 74 through the communicating channel 75. The oil pressure in the oil pressure chamber for timing advance 74 causes a displacement of the plunger 56 towards the housing 42 against the biasing force of the spring 57. Namely, the locking between the plunger 56 and the holder 55 is released.
While the locking is released, the position of the rotor 44 relative to the rotor 44 is varied and adjusted in either of the timing advance direction or the timing retard direction. The amount of the oil supply is adjusted by opening and closing of the oil control valve 80, which adjusts the oil amount in the oil pressure chambers 73, 74, so that the rotor 44 is rotated relatively to the housing 44. FIG. 27 shows the state that the rotor 44 is rotated up to the maximum timing advance position, to contact with a shoe 71 from the oil pressure chamber for timing retard 73 side. In this state, the vanes 64-67 of the rotor 4 are rotating. When the oil pressure in the oil pressure chamber for timing retard 73 is larger than that in the oil chamber for timing advance 74, the rotor 44 rotates relatively to the housing 42 in the timing retard direction.
As explained, the rotor 44 can be adjusted to rotate in the timing retard direction or in the timing advance direction relatively to the housing 42, by controlling the amount of oil to be supplied to the oil pressure chambers 73, 74. And the chip seals 46, 68 function to prevent the leakage of working oil between the oil pressure chambers 73, 74.
The oil control valve 80 is feed-back controlled by the electronic control unit 100, on the basis of the signals from a position sensor, which detects the rotation angle of the rotor 44 relative to the housing 42, and a crank angle sensor, which decides the output pressure of the oil pump 92.
The vane type hydraulic actuator of the prior art has a drawback, due to such a structure, that a biasing force generating means, for example, a spring 47 is necessary for pressing the chip seals 46, 68 for the tight contact between the vanes and the casing. This entails an increase of the number of the fabrication elements and the increase of the number of steps for assembling them. Thus the productivity is low and the production cost is high.
A complex mechanism, using an oil pressure delivery mechanism, for example, a slide plate 77, is necessary for releasing the locking means for suppressing the rotation, for example, a plunger 56. Namely the apparatus is complex, and productivity is low.